Field of the Invention
The present invention relates to a toner for developing an electrostatic latent image (electrostatic image) to be used in image forming methods such as electrophotography and electrostatic printing.
Description of the Related Art
In an image forming method based on electrophotography, image formation is performed by developing an electrostatic latent image on the surface of an electrophotographic photosensitive member with charged toner particles. The chargeability of toner needs to be controlled in order that satisfactory image formation may be performed.
In addition, a printer capable of forming an image having additionally high definition has been required in the recent market. Accordingly, the toner has been required to be capable of maintaining not only satisfactory chargeability but also high flowability for achieving high-efficiency development or transfer.
Against such background as described above, investigations have been vigorously made for improving the chargeability and flowability of the toner.
In general, a charge control agent is added to each of toner particles for controlling the chargeability of the toner. However, an investigation has been made on the utilization of the triboelectric charging characteristic of the binder resin of each of the toner particles.
Japanese Patent Application Laid-Open No. 2012-145600 describes a method of improving the electrical characteristics of toner with a polyester resin obtained by the polycondensation of a carboxylic acid component and a polyhydric alcohol component derived from a sugar alcohol. Japanese Patent Application Laid-Open No. 2012-145600 describes an alcohol having an isosorbide unit as one polyhydric alcohol component.
In addition, Japanese Patent Application Laid-Open No. 2012-233037 and Japanese Patent Application Laid-Open No. 2012-255083 each describe a toner improved in fixability, storage stability, and durability by using a polyester resin having an isosorbide unit. In addition, Japanese Patent Translation Publication No. 2012-521567 describes a toner using a polyester resin having an isosorbide unit from the viewpoint of environmental response.